<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>

<body>
    <script>
        //【1】无参数，无返回值
        let mao = function() {
            console.log("tst");
        }
        let mao = () => {
            console.log("tst");
        };
        //【2】无参数，有返回值
        let hai = function() {
            return 8;
        };
        hai = () => 8;
        //【3】有参数，无返回值
        let peng = function(a, b) {
            console.log(333);
        };
        peng = (a, b) => {
            console.log(333)
        };
        //【4】有参数，有返回值
        let sky = function(a, b) {
            return a + b;
        };
        sky = (a, b) => a + b;
        //
    </script>
</body>

</html>